Communication mechanism



y 1950 F. M. LINDLEY ET AL 2,515,561

COMMUNICATIONS MECHANISM Filed June 21, 1948 4 Sheets-Sheet l INVENTDR. flaw/r M Ll/VZJLE y ,eoaszr FEET TEE July 18, 1950 Filed June 21, 1948 v F. M. LINDLEY ET AL COMMUNICATIONS MECHANISM 4 Sheets-Sheet 2 [l jzr fi 7 INVENTOR. fiemwr M LMOL 5 BY IOBEETACEETTEE u y 1950 F. M. LINDLEY ETAL 2,515,561

COMMUNICATIONS MECHANISM Filed Jfine 21, 1948 4 Sheets-Sheet 5 JNVENTOR. Fzmv/r M L llvaL 5/ BY Eaaz-wrffsrrge y 50 F. MzLINDLEY ETAL 2,515,561

COMMUNICATIONS MECHANISM Filed June 21, 1948 4 Sheets-Sheet 4 ?atented July 18, 195 0 UNITED STATES PATENT. C

COMMUNICATION MECHANISM Frank M. Lindley, Cincinnati, andRobert F. Better, Richland County, Ohio Application June 21, 1948, Serial No. 34,304

7 Claims.

This invention relates to improvements in a communication mechanism and particularly to a mechanism for transmitting messages from a plurality of sending points or places to a given receiving point or station.

The invention will be illustrated and described in connection with one ofits uses, namely, in connection with a restaurant, eating establishment, or the like. In restaurants, eating establishments, and the like, there are arranged, so... called, stations,-each station comprising a plurality of places for individual patrons and. with each station in charge of a single attendant, waiter or waitress. The kitchen, bar, counter,

or the like, from which the station attendantfills;

the orders of the patrons, is generally remote from the station, thereby requiring the attendant to travel some distance for placing the order and. then returning to the station to take care of the needs of new patrons or the wants of the patrons,

who have given their order and while awaiting the filling of said orders. The attendant must subsequently return to the kitchen, bar, counter or the like to pick up the filled orders for serving same to the patrons.

The present invention contemplates the lacing or filling of the patrons orders without traveling to the kitchen, bar, counter, or the like thereby saving the time involved in order placement and enabling the attendant to more readily and quickly fill the patrons orders. rality of stations and a plurality of attendants it is necessary that the orders from different station attendants not be confused, which necessitates the several attendants knowing when the chaning points or stations to a single receiving point and which automatically notifies all sending points or stations when one of the stations or sending points is in operation that the mechanism is in use and for the other stations or sending points to attempt to use the mechanism would result in confusion at the receiving point.

In order to bring into practice the present invention use is made of transportable sending stations which are carried on the person of the attendant. .Transportabl e sending stations, as heretofore known, have required a plurality of batteries with the so called carbon microphones while the batteries may be combined or partially eliminated in the so called crystalmicrophones but which latter require additional vacuum tubes and auxiliary equipment. These microphones, and. the sending stations or transmitters, are therefore relatively heavy and by the present invention there is provided a transmitter or sending station that eliminates one battery or a. portion of a combined battery while using the carbon microphone.

g It is, therefore, another object of this invention to provide a simplified transmitter or broadcasting set having particular use with the presv ent invention.

With a plu-" nels of communication are clear so as not to attempt to file their order when another order is being placed and this invention contemplates means for preventing this confusion in transmitting and receiving individual orders. It is therefore the principal object of the pres-" ent invention to provide a communication system that will enable orders from a plurality of points to be transmitted to a single receiving point without interference with one another and Other objects and advantages of the present invention should be readily apparent by reference tothefollowing specification considered in conjunction with the accompanying drawings forming a part thereof and it is to be understood thatany modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

confusion between one another.

Another object of thisinvention is the provision of a communication mechanism for accomplishing the foregoing object in which subsequent users from remote stations are notified that the mechanism is in use and to transmit their order would result in confusion;

A further object of this invention is the provision of a communication mechanism for transmittin Orders from a plurality of separate sendand automatically upon the operation of a single sending station.

Fig. 5 is a wiring diagram of a receiver for 2. Sending station there being a receiver for each sending station.

Fig. 6 is a wiring diagram of a portion of Fig. showing a close connection between the receiver diagram of Figs. 4 and 5 instead of a remote relation as illustrated in said Figs. 4 and 5.

Fig. '7 is a wiring diagram of a pair of interlocks between two receivers and. which is a modification of the invention over that disclosed in Fig. 4.

Fig. 8 is awiring diagram of a sending or transmitting station in which use is made of but a single battery for energizing the microphone as well as operating the heater or filament of the tube.

Fig. 9 is a wiring diagram similar to Fig. 6 showing a close connection of the receiver diagram of Figs. 5 and 7 instead of the remote'connection thereof of said Figs. 5 and 7. I

Throughout the several views of the drawings similar reference characters are employed to denote the same or similar parts.

In general the present invention" contemplates a plurality of"Sendingstations'such as diagrammati'cal'ly illustrated in Figs. 2 and 3 and indicated in Fig. l by the reference numerals Hi; It, [0. and I'O' each being identical in-i-tsconstruction and operation. The transmitting stations it), It"; etc are of theportabletype-and one is carried by each attendant between the places of his customers or patrons; Thetransmitters HI, it; etc., are eachprovided a microphonel l' and an antenna HZ. (ioOperatingwi-th the several trahsmittersl-t; 13", it and" lil' are receivers t3; t3; W- and* F3 eachof which is substantially identical with the other. The receivers l3, 13, etc, are adapted to be fixedly mounted. somewhere-in the-establishment and each receiver is equipped with-areoeivingantenna i4. Associated with eachreceiveris an interlock respectively indicated by reference numerals *l 5,

55*, I5" and la -rmenerg-i'zingor operating asignal; associated therewith,-to show that it is in condition to be operated and torenderinoperative the other receivers'and their respective signals, said signals bcing-i-l-lustrated-i-n the drawing as' lights and indicated by the numerals 16, i6, I6" and 13"". Each of thereeiver's-Ifi; i3, [3 and I3 is suitably connected by-a wire, cable or the like, Hy, 'Fi, H" and H? with a single loudspeaker HP at the order're'ceiv-ing point such as a kitcherrbar, counter,- ontueuxe;

Since the transmitters-or sending stations l0, Hi etc;, are each'substantially--i'dentical, it is deemed sufficient if =b-ut"oneoftherrrb e illustrated and described indetail with particuiar reference to Fig. 2; As there shown the transmitter isa compact unit of the single tube variety-having-;the microphone H controlled by a manually-operable switch IS which completes; upon operation, a circuit to'the filament'or'heater flii of -the tube 2| through an A'-battery 22; this h'eatercircuit includes a wire 23 to a fixed contact 24-engageable by a movable contact 25 of theswitch I9. The circuit from the switch-contact ZEihcludes 'awire 26 to a second wire 21 extending from one side of the tube, while a wire 28' from the other side of the heater or filament; 20 extends to the other side of the A battery for thereby completing the filament or tube heater circuit;

The closing of the manuallyoperable switch l9 1 in addition toclos'ing contacts 2 and '25 also caused movable contact 29 to engage afixed contact 3il-thereby completing a circuitforfenergizing' the microphone, l I. This 'microphone circuit comprises a battery 3'! from one-side "ofwhich extends a wire 32 terminating in the microphone I I. Extending from the microphone l I is a wire 33 that terminates in the fixed contact 30 so that the circuit, upon engagement therewith of the movable contact 29, continues through the switch it, a wire 25, and a wire 35 to the secondary coil 36 of a transformer, indicated in its entirety by the reference numeral 33. The microphone circuit is completed by a Wire 38 from the other end of the secondary coil'33 to the other side of the battery 3|.

The transmitter or sending station IE! involves no particularly new mechanism but comprises, as readily understood, the usual sections such as the audio and modulation section enclosed in the dasli'li'ne box 39, the filament heating section enclosed in the dash line box 40 and the radio frequency oscillator section enclosed in the dash line box 4|. The radio frequency oscillator section includes the B battery 42 which has one side thereof connected to the primary coil of a transformer indicated in-generalby thereference numeral 43*. The said transformer 43 -terminates in the sending or transmitting antenna l2'.-

The modified transmitter in Fig-- 3. is what is known as a crystal microphone-which includes a pairof tubes H and} 24 A 'd ifie'ring" in characteristics as" iswell'known. With'this mechanism no microphonebatter-y cireuit is required wherefore the switch l-9-'-- has but a single movable contact 25- to' engage-thefi-xedcontact 24 forcompleting the A--" battery'circuittowach of 'the'two filaments ohheating elements. Theope'ration of the transmitter-of Fig. 3'isidentical withthat of Fig. 2-and comprises the same sections of audio frequency modulation tfl, filament-heating section 40 andradio frequency 'oscil'l'ation- 41.

The signals transmitted by the-sending stations are,- asnoted above, picked upby their receivers, l3, l3, l3" or 13 Asillustrated in Fig. 1, transmitter It is broadcasting or sendingamessage indicated bythe-wavy'l-ine 44 to the'receiver it Since eachof-= the receivers are-substantially identical it'is deemed suflicien-tit but one of them be described and illustrated.

Accordingly, there is illustrate'diin Fig. 5 a receiving set which-like the transmitter or sending station is divided up into standard sections. The receiver comprises the antenna connector secti'on 45, the radio-frequency amplifier section 46, the mixer and oscillator section 4-1, the intermediate frequency amplifier section 48, the detector section 49 and the au'dio'f-requency amplifi'er section 50: 1 ltis cleemed unnecessary to further' describe the -radio circuits" as they are standard andnot-limited te the particular elements shown'irr Figi' since-any receiveremploying conventional-circuits tuned to the frequency of its transmitter maybeemployedr" Each receiver-beyond the audio-frequency amplifier circuitis provided with" an audio or -loudspeaker sectionor circuit-indicated by the reference numeral- '5ifor bperatingthe loudspeaker 1a,; and it is in this circuit that the mechanism for operating the interlocks 15,15, etc. ,"0f the various receivers 13, |"3'f, -"etc ;,"is: located: The loudspeaker section, orgcircuit 5ljhas" entering therein a wire fromthe plate'of' the radio tube of the audio frequency amplifiersection or g: This relay switch may be positioned closely adjacent the output transformer 54 but" for convenience in illustration and description is illustrated separately from the receiver'circuit in Fig.5 with said relay switch and'parts associated therewith illustrated in Fig. 4. Accordinglyfthewire 55 is illustrated as 'terminati'ngin a terminal strip or plug 63 from which the co'nnection "to the relay switchis made. From theother end of the relay switch solenoid coil 59 is a wire that terminates in the terminal stripor plug 63 which-continues therefrom as a wire 51 terminating in one end of secondary coil 58 of a power transformer indicated in its entirety by-theflreference numeral 59, and through which secondarycoil 58 current is supplied to the said'wire" 52 and audio amplifier section or circuit radio'tube plate.

The power transformer 59 has its primary coil 69 connected by wires El and 62 to the terminal plug 63' from which extends'wires'fi land- 65 to a commercial current source, for example, 110 volts alternating current; "The wire Bl has therein the power switch 96,- mechanically coupled with the sensitivity control '66, for the entire receiver. It should be notedthat the power switch and sensitivity control may be and generally will be remote from the receiver.

The secondary coil 61 ofthe output transformer 54 has its ends connected by wires '68 and 69 to the terminal plug 63 from'which'extends wires 10 and H to the loudspeaker l8'and which wires. iii and H are indicated in Fig. 1 by the reference numeral ll similar wires from each of the other receiving sets or receivers tothe'loudspeaker being indicated byreference numerals ll, 11' and l'l', as above pointed out.

The operation of the device of the present invention up to this point is substantially well known, and briefly is as follows:

A plurality of compact battery powe'red radio transmitters HI, ID, etc., preferablyportable, are employed, each of which has conventional circuits therein under the control of its own manually operated push to talkswitch. The transmitters are of the short range one-way radio communication system type and each is adjusted or tuned to transmit on' its own frequency with each transmitter transmitting on a frequency different from each of the others. It will 'beunderstood thatthere may be any number of transmitters depending upon the area being covered;

A radio receiver l3, [3, etc., is employed with each transmitter with saidreceivers' each tuned 'to the frequency of its transmitter 10, 10', etc.

Each of the said receivers employs conventional 5;

push to talk switch IQ of anytransmitt'er, pro-,

Viding no .other' receiver and transmitter is in use, immediately effects the broadcast of aradio signal that renders inoperative to receivea radio signal all other receivers, as-will subsequently be made clear. ceivers the reception of a'radio signal causes an increase in current flow therethrough, resulting in an increase in current flow in'the wire 52 and thereforean increase of current flow in the solenoid coil 56" for operating the solenoid switchin the interlocks-l5, l5, etc., between the several receivers l3,-l3', etc., so that only the receiver receiving the transmitted signal will get into the loudspeaker it as will now be described. 1

As is customary in radio re- 94, 94, etc., is connected, respectively, by a wire Each of'the interlocks I5, 15'', etc., is substan tially identical with one anotherand is operated from the radio receiver with which it is associated. In the radio receiver. in Fig. 5, and as is customary with substantially all radio receivers, each, the radio frequency amplifying circuit 46, mixing and oscillating circuit 41, intermediate frequency amplifying circuit 48, detector .circuit '49, and audio amplifying circuit 59 is provided with a radio tube that includes a cathode and a plate between which flows current during the operation of the receiver. *Any one of these radio tubes may be employed in the operationof the interlocks of the receivers. As shown in the drawings, use is made of the radio tube 14 of mixer and oscillator section or circuit 41 in the "operation of said interlocks, It is to be understood that each of the receivers i3, l3', etc., is similarly From the terminal block 63 is'a'wire 89' into the interlock l5. The Wire 89" terminates in a connector strip 8| of the interlock l5 from which extends awire 82' to a fixed contactfi83' of a multi-contact solenoid switch indicated in itsentirety by the reference numeral 84.

Each of the other interlocks l5, l5" and iii is likewise connected with its receiver each having a wire 89, 89" and 89" which terminates in its terminal block or connector strip 9|, 8| and 8|" in-turn having a wire extending therefrom, 82, 8'3" and 82" respectively'terminating in a fixed contact 83, 83 and 93" ofthe multicontact solenoid switch 84; Eachof the fixed contacts 83, 83, 93" and 93" has a companion fixedcontact 85, 85, 85 and85 which are connected in parallel by a wire 86 with the ground indicated at 81. From this it will follow that each Y 0f the receivers l3, I3, etc., is provided with a common ground connection which is maintained -completed through the multi-solenoid switch through movable contacts 88, 88', 88" and 88" when the receivers are in readiness for operation but with no receiver receiving a signal.

Each of the interlocks l5, [5, etc., has associated therewith a signal l6; 16, etc., as noted above-and these signals are in the form of a lightbulb each having one side of its filament connected by a wire 89, 89', 99" and 89" with a wire 90 that extends from one side of a power source shown in the drawings as a battery 95. Each of the signal lights l6, l6, etc., has the other side of its filament connected, respectively, by a wire 92, 92, 92" and 92 with a fixed contact93, 93, 93 and 93" of the solenoid switch of its interlock l5, IE, etc., respectively, indicated in its entirety by the reference numerals 94, 94', 94" and 94". A companion fixed contact 95, 95', 95" and 95" of the solenoid switches 96, 9B, 96" and 96 with a common wire 91 that terminates at the other side of the power source or battery 9|.

spring biased or yieldably urged to its closed position by the spring I00 which is the normal posi pointedout above;

tion-zfo'r. maintaining; the? receiversinreadiness forfoperatiomat any and all .times.

Each zofatheinterlock solenoid switches 94;.84 etc; is; respectively, vprovided with a: fixed con.- tactil I", I01",- I01 and I 0 I f from each-of which extendsua wire I02, I02 I02-: and-I02 that terminates-in. the wire 80 from its receiver controlled radio tube radio tube 14, ,for example, as

Each of'the interlock solenoida switches 94-, 94 etc., has, respectively; a fi'xeducontactI05, I03, I03 and I03-"" thatrespectively: cooperates withthe fixed contacts I 0 I,

1014, etc.,andwhich companioncontacts- I03, 403, etc.,. each have, respectively, connected therewith one end of a-wire I04, I04, I04 and I04-'-"' that: respectively connect with wires- 96, 96,'.etc-'.,.and therefore the common wire 91. The common wire'91 has connected therewith one end ofva' wire I05 that has itsother end connected with wire 86 and therefore the ground81.

Eachof-the solenoid switches 94, 94", etc.,v includes a movable member I06, I06, I06" and I06 which carry respectively movable switch contacts I01'and I08, I01 and I08, I01" and I00" and;l01 and I08" the former connecting the-:fixed;contacts-93 and 95, 93' and 95, etc., while the latter connects the fixed contacts HH and I03,- IOI-' and. I03, etc. Associated with each of the movable members I06 and I06,- etc., respectively, of the solenoid switches, 94, 94, etc., is the solenoid coil 56, 55, .56 and. 56" for effecting the operation ofsaid switches with said movable members I06 and I06, etc., being held in their normal open position, respectively, byv a spring H0, H0", H0" and NW. Each'ofthe solenoid coils- 56, 56", etc., respectively, has. its ends connected. to terminals III and H 2, III and H2, III" and H2 and II-I' and 2' and to-whichterminals, respectively, extend wires 12 and 13,'-12'- and 13, 12" and13" and.12-'" and 13'! from the terminal-strips or terminal plugs 8|, 8|", etc., of the several interlocks I5, I5, etc. The said wires 12 and 13,12 and 13,-etc., each extends, respectively, as awire I41 and I48, I41 and'I48,I41" and I48 ",and'l41" and I4'8?""th at terminates in the terminal strip'or terminalplug 63 of-its receiver. The wire I41", see Fig. 5, isin efiect acontinuation of wire. 51' from the power transformer secondary coil. 58'..while.the wire I48 is in efiect a-continuationof the wire 53.Yf rom the output transformer primary coil' 53. From this it will be seen, as noted above, that the primarycoil 53 of output transformer.v andthe interlock solenoid switch coil 56 are in series with the output power transformer 59 and plate. of the audio frequencyampl'ifier section or circuit 50.

Continuing, now, with the. description of ."the operation of the device and assuming thatv the transmitter I0 is in use this operation is as follows:

The increase flow of current in the output transformer primary coil 53 and solenoid switch coil 56 causes a sufficient flow of current through the circuit or wires 12 and 13" to energize the said solenoid switch coil 56 for actuating its movable element I06 against the resistanceofthe spring I I0 thereby causing movable contacts I01 and I08 to complete the circuits, respectively, across fixed contacts 95 and 93 and; NW and. IOI The closing ofthe contacts-93". andn95 caused a completedcircuit from one end orsideof the power source or battery:'QI throughflthe'Wire 91, wire .96, fixed contact 95 movablecontact I01, fixedcontact 93; wire-92*, filamentofsignal light-16', wire 09', wire 90%including5 the multicontact solenoid switch solenoid coil 99 to the other-end or. side of the current source or battery 9i: This resulted-in theillumination of the signal light: I6 and satsthe same time interrupted the common-ground circuit to each ofthe receivers by openingfixed contacts 83 and 85, 83 and 85, etc. thereby disabling each of the receivers. However, at the time of closing the contacts 93' and-:95", astnoted -above, the contacts IOI and I03'. were closed thereby reestablishing the ground circuit-for the cathode of radio tube 14 of radio-receiver- I3 as follows, from wire 80,.Fig. 5;wire00, Fig. 4,. through wire I02, fixed contact I 0 I ,movablecontact I 08', fixed contact I03, wires-I04" and 96-, and wires 91 and I05 to the ground 81 wherefore the receiver I3 is maintained in operationso that the Signal from the transmitter I0 will be. delivered to theaudio or loudspeaker I8 while any signalattempted from any. oneoftheothertransmitters I0, I0 and I0 will not be transmitted through itsreceiver to the audioor loudspeaker.

v It wi-lLbe .noted in Fig. 1 that the sending station or transmitter I0 and the receiver I3 are illustrated in phantom lines and it will further be noted. that the interlock I5' in Fig. 4' is similarly illustratedin phantom lines. In Fig. 4, also,.the fixed'contacts\83- and 85" alongwith their. cooperating. movable contact 88?" of the multi-contact solenoid switch 84 are similarly shownnin-phantom .lines.. The reason for this is to. illustrate that any number of receivers and interlocks maybeemployed it being merely necessary', to add-additional contacts,.both movable and fixed-,to the solenoid switch 84 for each additional receiver and its interlock. It is of course understood that a separate sending. station or transmitt'er- I0lwill' be requiredfor each of the additional receivers .with saidtransmitters or send- .ingstationsand. receivers tuned to one another andldiif'eringi from eachother-and those in use.

Connected across the terminals III and H2, I II fandQI'IZi', etc., of .each of the solenoid switch coils 56, 56, etc., is anadjustable or variable condenser I49, I49, I49 and I49 which is employedas atiiner. for effecting a delay in the return of ithe solenoid switches 94, 94, etc., to their normal positions'thereby' preventing the disconnection of the radioreceiver presently being used from the loudspeaker as,.for example, should the user-v inadvertently open his push to talk transmitter switch and another user desiringito utilize his. sending. station. or transmitter close his switch. In other. words, this time delay. is be- ,lieved desirable. toinsure the user completing his use before-someone else disconnects his receiver from the speaker andto safeguard against human error .in the. use of 'the system. It is understood that thistime. delay is relatively small in the matter 1 of Iseconds in time.

The-,illustration-=in-Fig. 6 discloses the method of, closely connecting or coupling the interlock relay switch 94- with the receiverinstead of having: the" sameremote therefrom and connected .with the receiver-terminal strip or terminal plug.

BYj'thiS construction the'wire 55 is connected directly-with-the solenoid coil 56' instead ofto the terminal= strip or terminal plug 63 :andfrom thereconnected with the terminal strip or terminal 'plug; 8I of the interlock. At the same time theother endofthe solenoid coil 56 is directly,v connectedwith the wire 51 from the output transformer sec'ondary'coil 58, again insteadof through the-terminal strips or terminal plugs 8| and 63 as is fullyobvious fromFig. 6.

In the modified inter-lock mechanism of Fig. '1 the multi-solenoidxswitchr84 has been eliminated utilizing insteadithe solenoid switch of the several interlocksffor disabling the other. receivers and for operating a'signaI to indicate the re- 7' ceiver-that is in use. 'Thisgparticular arrangementr-isadvantageous-at such timeswhen only twotreceivers arerbeingem'ployed wherefore the said interlock 'are illustrated as employing but two devices; but iit'is .to .be understood that this -modified= iarrangementwmay be employed with additional receive'rsr 0.: a Inthemodifiedinterlocks of Fig. '7 single pole double throw switches I25 and: I25 are utilized instead ofthei-double-poledouble throw switches -94,.94,etc., of Fig. 4. In this) construction each of lthetswitch coils 55a and 56b is employed to energize, respectively, a magnetql I3, and H3, as is usual with single pole double throw switches.

Eachlof the magnets II3x-.and' H3 is adapted to operate a movable switch contact or switch blade H4 and H4 of its relay switch I25 and I25, respectively; The switch blades H4 and H4 are respectively movable between fixed contacts I24 and-I28 andzl24' and I28. The movable switch elements'or switch blades I I4 and H4 are connected with lone another by a wire I21 which in turn is connected withthe ground 81.

'Therelay switch I25 has. extending from its .fixe'dcontact 124a wire I22 terminating in its terminal strip' or, terminal block I20 while the relay switch; I25 similarly has extending from its'fixed-contact l24' a wire I22 that terminates in its terminal strip 'or terminal plug I20. Ex-

tendingfrom :the terminal strip or terminal plug I20; asa continuation'of wire I22,-is a wire I23 that terminates: in. the terminal strip or plug I 20"'of the relay switch I 25. Extending from the 'terminal strip Or::terminal plug I20 as a constripor terminal plug I20 of relay switch I25.

From .the term-inalstrip'or terminal plug I20, as a continuation of wire I 23", is a wire 80a that I goes. to the firstreceiver as wire 80 in Fig. 5 while the wire 801) goes to the second receiver again as wire 80 in .saidFig. 5. r

-. Withttheparts; in this positionthe radio tube 14 of the receivers each has its cathode connectednthroug'hsthe interlock of the other receiverito thegroundp This circuit being as follows, through wire 80, Fig. 5, wire 80:1,,Fig. '7, to 'the terminal strip. orterminal plug I20 of the relaylswitch I25, wire I23, terminal strip or terminal plug 1.20; wire-I22, fixed contact I24, movable'contact H4. and wire I21 to the ground 31.. The radio tube 14 of the second receiver is similarly connected through the wire 80, Fig. 5, wire 80b, Figi'l, to the terminal strip or terminal plug I20, wire I23; terminal strip orterminal plug I20, wire I22, fixed contact I24, movable :contact H4 and wire I21 to the ground 81.

From thisit willbeseen that actuation of the movable switch member or bladegl I4 or II4 of the receiver being energized interrupts the ground connection ofthe other receiver thereby rendering said other receiver-inoperative to receive signals.

The actuation of either of these movable contacts or switch blades H4 and H4 automatically completes a circuit through the second contact of its interlock solenoid switch I25 and I 25 ,for

lighting the signal of the receiver being used. To accomplish this the fixed contacts I20 and I28, respectively, have extending therefrom a wire I 29 and I20 which terminate, respectively, in terminal strip or terminal block I20 and I20. Extending from the terminal strips or terminal blocks I20 and I20, respectively, as continuations, respectively, of wires I29 and I 29 are wires I33 and I33 which terminate in one end of filaments of signals, respectively, I34'and I34. The other ends of the filaments of signals I34 and I34 have respectively connected therewith wires I35 and I35 which terminate in a common wire I36 extending to one end or side of a power source or battery I31. The other side of the power source or battery I31 has extending therefrom a wire I38 from which extends wires I39 and I39 respectively terminating in the terminal strip or terminal plug I20 and terminal strip or terminal plug I20. Extending from the terminal strip or terminal plugs I20 and I 20, respectively, as continuations of wires I39 and I39, respectively, are wires I40 and MI which are connected to the movable switch elements or switch blades H4 and H4, conveniently shown in the drawings as connected with the wire I21 ahead'of the switch element or switch blades H4 and. H4.

The operation of the interlocks of '7 is believed obvious-from the foregoing description and the lighting or energizing of the signals I34 and I34 is believed likewise obvious from Fig. 7. Specifically, the circuit for the signal light I34 is as follows, the circuit for the signal light I34 being identical except for the addition to the reference numerals of a prime The closing of the switch element or blade I I4 with the fixed contact I28 causes a current fiow from one side of the power source or battery I31 through wires I36 and I35, filament of signal light I34,wires I33 and I29, fixed contact I28, movable contact or switch blade II4, a portion of wire I21, and wires I 40, I39 and I38 to the other side of the power source or battery I31.

The illustration in Fig. 9 discloses the close coupling of the modified interlocks of Fig. '7 with the receiver and which is accomplished in substantially the same manner as above described in connection with Fig. 6. The parts in Fig. 9 are identified by the same reference characters as illustrated in Fig. 7 wherefore it is believed no I further description of Fig. 9 is necessary.

As was noted above, sending stations or portable microphones as heretofore known and used have considerableweight which is occasioned by the necessity of batteries in each of the circuits or by additional vacuum. tubes and auxiliary equipment resulting in a device that may be quite tiring to the attendant in his transportation of same throughout the day. To overcome this difiiculty use may be made of the transmitting station or microphone illustrated in Fig. 8 which, by comparison with Fig. 2, has eliminated therefrom the battery 22 with suitable connections for providing an operative structure.

Specifically, the mechanism of Fig. 8, as distinguished from that in Fig. 2, comprises a filament or heater 20 from one side of which extends a wire 21 that terminates in a wire 26 connected to the movable contacts 25 and 29 of the push to talk switch I9. I

The switch movable-contact 25 is adapted to engage the fixed contact 24 from which extends a wire I42 which-terminates at its other end in the positive pole of a battery I43. The other "to talk switch t9.

side or negative ole. of the battery t4-3 has connected therewith a wire 1M4 thatrterniinates in one end ofmheksec'ondarymoil 38 :of:d;ransformers-"I. "The other end of the secondary coil .36 has connected: therewith: one end of a wire i4 5 that terminatesin the r carbon -microphone I I and from whichextends a wire 93: to a fixe'd switchcontact me :that cooperates with and-' 1s engaged by the :movablc-contact' m of the push Connected with the wire M4 ahead-of: the-secondary coil35 of-the transiormer 31 is-a wire I 46 that terminates intheoth'er-end 'oi the heater or filament 21) of tube 21.

- the forego'ing, it will be noted that e single battery I 43 of a capacity. and size no greater than either of thebatteries' 22 and :3I is employed for energizing the microphone circuit and the tube'heater or filament circuit. The microphone circuit comprises from one side of the battery "I43 :aw'ire Id'2, -contactsi24 and :25, switch I9, contacts z a :and 30,- w-ire .33, mi-crophone II, wire cl15,::transiormensecondary coil 36 and wire 4 M to the other side of the battery I43. The *filament :or heater circuit' includes tacts 24 and25, switch 13, wires 26 and-"2'1, filament or heater 20, and wires l is :and t back to the other side of the'ba'ttery Hi3.

In order that the'sending station of Fig. 8 operate it is necessary that the positive side ofthe battery I43 be connected with the positive side of the filament as wellas the positive-side of the microphone II so that satisfactory results be obtained.

From the foregoing, it is'believed now evident that there has been provided a short range communications system utilizing standard radio equipment and in which a plurality of sending or broadcasting and receiving stations with a single audio or loudspeaker are employed with said receivers being interlocked so that when any one of them is in use the-others are rendered inoperative whereby only the operating receiver has its signals connected with the-audio or loudspeaker.

What is claimed is:

'1. In a device of the class described the combination of a plurality of transportable radio sending stations each adapted to broadcast on a diiferent radio irequency,-a-receiving station for each broadcasting-station tuned-to the radio frequency of its broadcast-ingstation,-a-single loudspeaker connected with each of the receiving stations, an interlock associated-with each i'enection oi the radio tubeof-each-receivcrexcept that of the receiver in operation.

2. In a device of the class described the combination of a plurality of transportable radio sending stations each adapted to broadcast on a different radio frequency; a receiving station for each broadcastingstation tuned'to the radiofre- 12 quency'of its broadcasting station, sasingle loudspeakericonnected with-each or the-receiving stations, an interlock associated with 'each receiving station connected with-each ofthe otherrreceiving stations and operable uponaenergization of its receiving station for rendering inoperative-allot the other receiv'ing stations, a signal lighti'associated with each radio'receivingstation interlock and operable" simutaneously therewith for indicatingsaid receiving station is in operation; each of the radio'receivers including a radio tube. .having a cathode element including a :ground connection, each interlock aforming :azpart of the ground connection "of the cathode element oi! the radio tube, andmeansfinrrsaid interlock operable for breaking the ground connection of the radio tube of each'receiver: except that of-the receiver in operation, comprising a solenoid operated switch for completing the ground connection of the radio tube of the receiver incoperation simultaneously with the breakingof the said-ground connection of the othertreceivers.

3. In a device ofthe class-*describedlthe combination of a 'pluralitycf transportable-radio sending stations each adapted to broadcast on ta-dif- 'feren't radio frequency, a 'receiving station ior each broadcasting ."station-tune'd :ito 'thefradio' frequency of its broadcasting station, a single loudspeaker connected-with eachrof'the receiving stations, an interlock associated-with eachmeceiving station connected =with each of the'otherxreceiving stations --andoperable upon energization 20f its receivingstation for renderingfinoperativeall of the other receiving stations; a signal 'light associated 1 with each vradio receivin'g station' interlock and operable simultaneously therewith for indicating said receiving station is irroperation, each of the radio receivers including-a radiotube having a cathode "element including a ground connection,- each interlock forming azpart oi the ground connection of the cathode element of'the radio tube, Y and meansiinsaidinteflock operable for breakingthe groundconnection of'the radio tube of each receiver except that of-the receiver -in operation, comprising a solenoid operated switch common to all or 'the'receivers :for'normal- 'ly maintainingtheir groundconnections operable upon the energizatiomof any one of thereceivers for breaking the ground connection of wall 'reall of the other receiving stations, *each of the radio receivers including a 'radiotube' having a cathode element including a ground connection, each interlocktiorming apart orthe"groundcconnection of'the cath'ode'element of the radio tube, and means in said "interlock operable-for breaking the ground connectionof the radio 'tube of each receiver except that of the receiver in :operation.

5. In 'a device of the. class" described-themom-bination of a pair 'of transportable radiossending stations each ada zzte'datobroadcast:onvazdifferent radio frequency, a receiving station for each broadcasting station tuned to the radio frequency of its broadcasting station, a single loudspeaker connected with each of the receiving stations, an interlock associated with each receiving station connected with the other receiving station and operable upon energization of its receiving station for rendering inoperative the other receiving station, each of the radio receivers including a radio tube having a cathode element including a common ground connection, the interlocks together forming a part of the common ground connection of the cathode elements of the radio tubes, and means in each of said interlocks operable for breaking the ground connection of the radio tube of the other receiver when its receiver is energized.

6. In a device of the class described the combination of a pair of transportable radio sending stations each adapted to broadcast on a diiferent radio frequency, a receiving station for each broadcasting station tuned to the radio frequency of its broadcasting station, a single loudspeaker connected with each of the receiving stations, an interlock associated with each receiving station connected with the other receiving station and operable upon energization of its receiving station for rendering inoperative the other receiving station, each of the radio receivers including a radio tube having a cathode element including a common ground connection, the interlocks together forming a part of the common ground connection of the cathode elements of the radio tubes, and means in each of said interlocks operable for breaking the ground connection of the radio tube of the other receiver when its receiver is energized, and a signal light associated with each radio receiving station interlock and operable simultaneously therewith for indicating said receiving station is in operation.

7. In a device of the class described the combination of a pair of transportable radio sending stations each adapted to broadcast on a different radio frequency, a receiving station for each broadcasting station tuned to the radio frequency tubes, and means in each of said interlocks operable for breaking the ground connection of the radio tube of the other receiver when its receiver is energized, including a solenoid operated switch for breaking the common ground connection of the radio receiving stations and establishing a ground connection for its radio receiver upon energization thereof.

FRANK M. LINDLEY.

ROBERT F. BETTER.

EEFERENQES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,326,727 Hammond Dec. 30, 1919 1,356,488 Compare Oct. 19, 1920 1,934,211 Schroter et al Nov. 7, 1933 2,081,625 Goldsmith May 25, 1937 2,158,516 McIntosh May 16, 1939 2,187,603 Hall Jan. 16, 1940 2,210,089 Loughren Aug. 6, 1940 2,214,101 Cunning Sept. 10, 1940 2,249,425 Hansell July 15, 194] 2,289,485 Cover -1 July 14, 1942 2,290,992 Peterson July 28, 1942 2,292,222 I-Iaigis Aug. 4, 1942 2,383,908 Bowers Aug. 28, 1945 2,454,022 Yardeny Nov. 16, 1948 2,458,558 Bradley Jan. 11, 1949 2,469,555 Hitchcock May 10, 1949 

